1. Field of the Invention
The present invention is directed to a process and an apparatus to form a continuous fin helically around the exterior of a cylindrical tube.
2. Prior Art
The process and the apparatus to manufacture helically wound fin tubing is well known in the art. Examples in the prior art of fin tubing include the patents to A. H. McElroy, U.S. Pat. Nos. 3,388,449; 3,500,903; and 3,613,206. The resulting fin tube is utilized in heat transfer applications where a fluid or gas may be passed within and through the tube. Heat transfer is accomplished by transfer of heat through the fins. Fin tubing finds many applications from air conditioning units to refrigerators to many industrial applications.
It is known that if the fin is helically wound tightly around the tube, it will provide a good heat transfer surface without fastening, bonding or otherwise affixing the fin around the tube. It has been found, however, that in order to properly wind the fin to the tube, the first: few revolutions of the fin must be secure to the tube, otherwise, the remaining length of tubing will not be properly affixed thereto.
Existing solutions to this problem include stapling the first fin or few fins at the initial end of the tube or manually curling these initial fins tighter. Optionally, the last few fins at the end of the tube may also be pulled down or stapled to assure a tight fit.
These procedures require additional time and expense to secure the fin at the end of the tube and require additional human intervention and personnel to secure the first few revolutions of the fin to the tube.
Accordingly, there is a need to secure the initial revolutions of the fin to the tube without manually tightening the fins to the tube.
It has also been found that it is advisable to orient the primary forming roller and the spindle roller such that the tip of the fin is thinned in relation to the base of the fin. This promotes the curling of the fin around the tube during the metal forming process. At the same time, if the fin is curled too tightly, the end of the fin will buckle and wave.
Accordingly, there is a need to prevent buckling and waving of the end of the fin tube by controlling tightness of the fin to the tube.